1. Field of the Invention
The present invention relates to a parity generating apparatus for generating a parity bit in order to improve a decoding performance in turbo decoding, and an MAP apparatus.
2. Description of the Related Art
An error correction technique using a turbo code was first published by Claude Berrou in 1993, opening a new chapter in the error correction field. The error correction capability of the turbo code has characteristics such that a BER (Bit Error Rate) performance is improved according to the number of repetitions thereof. In addition, it has been known that a sufficient amount of repetition would achieve a level of error correction as close as the channel capacity method presented by C. E. Shannon.
A turbo decoder is implemented based on a MAP (Maximum A Posteriori) algorithm or a SOVA (Soft Output Viterbi Algorithm). In general, in terms of calculation complexity, a turbo decoder using the MAP scheme is two to four-fold more complicated than the turbo decoder using the SOVA scheme, and has a better BER by 0.5 dB to 0.7 dB in terms of performance.
Recently, a turbo coder and turbo decoder have been adopted for a system aimed at a high speed data transmission requiring a low BE, such as an LTE (Long Term Evolution) standard, a next-generation mobile communication system, or the like, as well as the existing mobile communication system, and also adopted as a standard in an error correction field of a digital broadcast communication system.
Meanwhile, S. S. Pietrobon has proposed a turbo decoder having a structure using a corrected LogMAP algorithm obtained by simplifying a LogMAP scheme so as to make it easily implementable by hardware. In this case, because the implementation of the existing LogMAP scheme has a complicated configuration, a SubLogMAP scheme, a MaxLogMAP scheme, and the like, have been also proposed in order to reducing the amount of calculation, while submitting to degradation of performance.
S. S. Pietrobon has simplified the existing LogMAP algorithm by using an E function.